1. Field of the Invention
This invention relates to compositions including organosiloxane polymers containing sulfur and to a method of forming higher molecular weight products from such compositions. This invention also relates to organosiloxane gels, elastomers and resins containing sulfur.
2. Description of the Prior Art
Compositions containing mercaptoorganosiloxanes free of any vinyl functionality which are polymerized by means of the mercapto groups to resins and sealants are known in the art. For example, in U.S. Pat. No. 4,133,939, Bokerman and Gordon teach a method of coating a substrate with a silicone release coating involving the radiation cure of mercapto-functional polydiorganosiloxane fluids mixed with a sensitizer such as benzophenone. While a radiation curing mechanism is rapid and provides one-package systems which are stable in the absence of heat and light, it is useful only for relatively thin coatings and requires a high intensity radiation source such as ultraviolet light or electron beams.
Peroxide cure of mercaptoorganosiloxanes free of vinyl unsaturation is also known, as is demonostrated by Homan and Lee in U.S. Pat. No. 4,070,329. In that patent, the patentees teach mixtures of mercaptoorganopolysiloxanes, organic peroxides and, optionally, a filler to provide a composition which cures at room temperature or by heating to form elastomers which are useful as sealants and rubber articles. Likewise, Homan and Lee in U.S. Pat. No. 4,070,328 claim the use of mixtures of mercaptoorganopolysiloxanes, organic hydroperoxides, a nitrogen compound and, optionally, a filler to produce a composition which cures at room temperature to elastomers which are useful as sealants and rubber articles. However, the above compositions are not one-package systems, since the polymerization or cure begins immediately upon mixing the ingredients.
Vanderline, in U.S. Pat. No. 3,445,419, teaches the production of a type of mercapto-functional copolymer consisting of organosiloxanes with mercapto-functional organic compound segments which are prepared by grafting a mercapto-functional carboxylic acid ester such as pentaerythritol tetrakis(3-mercaptopropionate) onto a vinyl-terminated organosiloxane. When an alkaline catalyst such as an amine is added to the resulting graft-copolymer, there is obtained a composition which is stable in the absence of air, but cures to an elastomer at room temperature upon exposure to air. However, this patent does not suggest the use of metal carbonyl compounds as catalysts for the room temperature polymerization or cure of the compositions hereinafter described.
Nametkin, et al., in the Journal of Organometallic Chemistry, 149 pp. 355-370 (1978) report that when stoichiometric amounts of Fe(CO).sub.5, Fe.sub.2 (CO).sub.9, or Fe.sub.3 (CO).sub.12 are reacted with thiols of the general formula RSH, where R is an alkyl or aryl radical, in solution, a complex {RSFe(CO).sub.3 }.sub.2 and a small amount of the disulfide, RSSR, is produced at room temperature and that Fe.sub.3 (CO).sub.12 is the most effective catalyst. Thermal decomposition of the complex in n-dodecane solution at 160.degree. C. in the presence of air results in decomposition of the complex to form the disulfide. However, this article does not teach that Fe(CO).sub.5, Fe.sub.2 (CO).sub.9 or Fe.sub.3 (CO).sub.12 will function as a catalyst in non-stoichiometric amounts for the room temperature polymerization or cure of the compositions hereinafter described.